1. Field of the Invention
The invention concerns a process for the production of a plasticized polyvinyl butyral particularly used for gluing a base onto glazing, especially a base intended to attach an interior rearview mirror to a windshield.
2. Background of the Prior Art
Polyvinyl butyral (PVB) which is plasticized using adequate plasticizers is known to be used in the form of films, as an intermediate layer in laminated glazings. It is also used for gluing articles to sheets of glass, particularly bases for rear-view mirrors. This latter application requires different properties from those properties required for the application of PVB as an intermediate layer between two sheets of glass. In particular, plasticized PVB for gluing bases must have great rigidity, resistance to high temperatures, that is approximately 80.degree. C., very good adhesion in view of the forces to which the base can be subjected during adjustment of the rear-view mirror of a vehicle, which occurs under extremely varied temperature conditions.
Known polyvinyl butyrals used for this application are not entirely satisfactory; in particular, the adhesion can be poor or insufficient at high temperatures.